This research project examines the use of smokeless tobacco among adolescents and the role this plays in the development of cigarette smoking. The proposed research will longitudinally and experimentally assess the relationship between chewing tobacco use and smoking for a wide age range of subjects. The proposed research is divided into two components. Component I will combine an experimental evaluation of smoking prevention programs with an in-depth longitudinal study of the development of both smikeless tobacco use and cigarette smoking. Component II experimentally analyzes the potential of smokeless tobacco to promote cigarette smoking. The prevention program for 7th and 9th grade students will compare two curriculums: smoking prevention only and tobacco chewing prevention plus smoking prevention. Treatments are compared with each other and a control group to assess whether the addition of anti-chewing materials increases the effectiveness of the prevention program by deterring smoking. The in-depth facet of Component I assesses students in grades 6 through 11 to identify cross-sectional and longitudinal predictors of smokeless tobacco use and smoking. Questionnaire and physiological measures are used to evaluate the full sample of 4,000 students over a three-year period. A subsample of 384 students from both control and and treatment conditions is studied in depth using interviews, telephone probes, parent interviews, and parent-child interaction tasks. The longitudinal study of both the full sample and in-depth subsample will provide information on the social processes involved in initiation of either smoking or chewing, and the influence that use of one substance has on promoting subsequent use of the other. Component II experimentally analyzes the potential of smokeless tobacco to promote cigarette smoking. There are three studies proposed which are designed to assess the effects of deprivation of either cigarettes or chewing tobacco on serum nicotine levels or cravings. For subjects who use both substances the studies examine the effects of deprivation of one substance on the topography and rate of consumption of the substance. An additional study examines the effects of deprivation of a tobacco product on the subject's cravings in their natural environment. This experimental analysis of the relationship of chewing tobacco and cigarette use will empirically determine the effects of using chewing tobacco on the probability one subsequently becomes a smoker.